Try this security setup it will use less resources then either of those:
I suggest you run 1 Anti-virus program/ 1 Firewall/ and a combo of anti-spyware

Firewalls
Here are some firewalls which are free for personal use and most commonly used:Comodo <-Vista CompatibleKerio (sunbelt) <- vista compatibleOnline ArmorZonealarm <-Vista Compatible I recommend this one